// ==========================================================
// FreeImage 3 .NET wrapper
// Original FreeImage 3 functions and .NET compatible derived functions
//
// Design and implementation by
// - Jean-Philippe Goerke (jpgoerke@users.sourceforge.net)
// - Carsten Klein (cklein05@users.sourceforge.net)
//
// Contributors:
// - David Boland (davidboland@vodafone.ie)
//
// Main reference : MSDN Knowledge Base
//
// This file is part of FreeImage 3
//
// COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN "AS IS" BASIS, WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES
// THAT THE COVERED CODE IS FREE OF DEFECTS, MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE
// OR NON-INFRINGING. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE COVERED
// CODE IS WITH YOU. SHOULD ANY COVERED CODE PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT
// THE INITIAL DEVELOPER OR ANY OTHER CONTRIBUTOR) ASSUME THE COST OF ANY NECESSARY
// SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL
// PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED HEREUNDER EXCEPT UNDER
// THIS DISCLAIMER.
//
// Use at your own risk!
// ==========================================================

// ==========================================================
// CVS
// $Revision: 1.5 $
// $Date: 2009/09/15 11:47:46 $
// $Id: FreeImageStreamIO.cs,v 1.5 2009/09/15 11:47:46 cklein05 Exp $
// ==========================================================

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace FreeImageAPI.IO
{
    /// <summary>
    /// Internal class wrapping stream I/O functions.
    /// </summary>
    /// <remarks>
    /// FreeImage can read files from a disk or a network drive but also allows the user to
    /// implement their own loading or saving functions to load them directly from an ftp or web
    /// server for example.
    /// <para/>
    /// In .NET streams are a common way to handle data. The <b>FreeImageStreamIO</b> class handles
    /// the loading and saving from and to streams. It implements the functions FreeImage needs
    /// to load data from an arbitrary source.
    /// <para/>
    /// The class is for internal use only.
    /// </remarks>
    internal static class FreeImageStreamIO
    {
        /// <summary>
        /// <see cref="FreeImageAPI.IO.FreeImageIO"/> structure that can be used to read from streams via
        /// <see cref="FreeImageAPI.FreeImage.LoadFromHandle(FREE_IMAGE_FORMAT, ref FreeImageIO, fi_handle, FREE_IMAGE_LOAD_FLAGS)"/>.
        /// </summary>
        public static readonly FreeImageIO io;

        /// <summary>
        /// Initializes a new instances which can be used to
        /// create a FreeImage compatible <see cref="FreeImageAPI.IO.FreeImageIO"/> structure.
        /// </summary>
        static FreeImageStreamIO()
        {
            io.readProc = new ReadProc(streamRead);
            io.writeProc = new WriteProc(streamWrite);
            io.seekProc = new SeekProc(streamSeek);
            io.tellProc = new TellProc(streamTell);
        }

        /// <summary>
        /// Reads the requested data from the stream and writes it to the given address.
        /// </summary>
        static unsafe uint streamRead(IntPtr buffer, uint size, uint count, fi_handle handle)
        {
            Stream stream = handle.GetObject() as Stream;
            if ((stream == null) || (!stream.CanRead))
            {
                return 0;
            }
            uint readCount = 0;
            byte* ptr = (byte*)buffer;
            byte[] bufferTemp = new byte[size];
            int read;
            while (readCount < count)
            {
                read = stream.Read(bufferTemp, 0, (int)size);
                if (read != (int)size)
                {
                    stream.Seek(-read, SeekOrigin.Current);
                    break;
                }
                for (int i = 0; i < read; i++, ptr++)
                {
                    *ptr = bufferTemp[i];
                }
                readCount++;
            }
            return (uint)readCount;
        }

        /// <summary>
        /// Reads the given data and writes it into the stream.
        /// </summary>
        static unsafe uint streamWrite(IntPtr buffer, uint size, uint count, fi_handle handle)
        {
            Stream stream = handle.GetObject() as Stream;
            if ((stream == null) || (!stream.CanWrite))
            {
                return 0;
            }
            uint writeCount = 0;
            byte[] bufferTemp = new byte[size];
            byte* ptr = (byte*)buffer;
            while (writeCount < count)
            {
                for (int i = 0; i < size; i++, ptr++)
                {
                    bufferTemp[i] = *ptr;
                }
                try
                {
                    stream.Write(bufferTemp, 0, bufferTemp.Length);
                }
                catch
                {
                    return writeCount;
                }
                writeCount++;
            }
            return writeCount;
        }

        /// <summary>
        /// Moves the streams position.
        /// </summary>
        static int streamSeek(fi_handle handle, int offset, SeekOrigin origin)
        {
            Stream stream = handle.GetObject() as Stream;
            if (stream == null)
            {
                return 1;
            }
            stream.Seek((long)offset, origin);
            return 0;
        }

        /// <summary>
        /// Returns the streams current position
        /// </summary>
        static int streamTell(fi_handle handle)
        {
            Stream stream = handle.GetObject() as Stream;
            if (stream == null)
            {
                return -1;
            }
            return (int)stream.Position;
        }
    }
}